ALBERT

Description: A continuous countercurrent supercritical CO 2 extraction-distillation dual-column process was developed to extract and concentrate natural vitamin E (VE) from soybean oil deodorizer distillate (SODD). The experimental results demonstrated that process parameters such as extraction pressure, temperature, and solvent-to-feed ratio significantly impacted on the extraction efficiency of natural VE. A new five-parameter mass transfer model for the continuous countercurrent supercritical CO 2 extraction-distillation dual-column process was presented based on the Penetration and Double-Film theories. The calculated values of the mathematical model agreed well with the experimental data, with absolute average relative deviation values of less than 25 %. A continuous countercurrent supercritical CO 2 extraction-distillation dual-column process was developed to extract and concentrate natural vitamin E from soybean oil deodorizer distillate. A new five-parameter mass transfer model for this process was presented based on the Penetration and Double-Film theories.

Description: Fluid flow and particle collision intensity in a rotating-drum bioreactor are investigated by numerical simulation and a conventional stirred-tank bioreactor is selected for comparison. Fluid flow is simulated by the computational fluid dynamics (CFD) software package FLUENT® whereas particle collision intensity is approached numerically through a hard-sphere model. The dissipation rate of turbulent kinetic energy and the maximum particle collision intensity in the rotating-drum bioreactor are about one order of magnitude smaller than those in the stirred-tank bioreactor. The rotating-drum bioreactor is likely to have a less severe impact on bioleaching microorganisms, and thus is expected to have great potential in the field of bioleaching processes. Rotating-drum bioreactors provide excellent gas-liquid mass transfer, low power consumption, and potential for bleaching processes. The critical particle collision intensity is calculated by simulating the collision process of the individual solid particles with each other. Its maximum collision intensity in the rotating-drum bioreactor is ∼1/10 of that in the conventional stirred-tank bioreactor.

Description: [1]  Pesticides have adverse effects on human health and the environment and can be transported through the atmosphere from application sites and deposited to sensitive ecosystems such as the Arctic and the Great Lakes. This study used a comprehensive multimedia regional pesticide fate and chemical transport modeling system that we developed to investigate the atmospheric transport and deposition of toxaphene to the Great Lakes. Toxaphene was never heavily used around the Great Lakes and was banned in North America by 1993; however, toxaphene concentrations in fish and water in the Great Lakes are still high, resulting in fish consumption restrictions for the Great Lakes. Simulated results predict a significant amount of toxaphene (~350 kg) being transported through the atmosphere and deposited into the Great Lakes in the simulation year. Results also show that U.S. residues and global background concentrations are major sources to toxaphene deposition into the Great Lakes and atmospheric concentrations in the region. While the U.S. residues are the dominant source in warm months, the background dominates during winter months. In addition, different sources have different influences on the individual Great Lakes due to their proximity and relative geographical positions to the sources; U.S. residues are the dominant source to Lakes Ontario, Erie, Huron, and Michigan, but they are a much less important source to Lake Superior. These results shed light on the mystery that observed toxaphene concentrations in Great Lakes' lake trout and smelt declined between 1982 and 1992 in four of the Great Lakes except Lake Superior. While monthly total depositions to Lakes Ontario, Erie, Huron, and Michigan have clear seasonal variability with much greater values in April, May, and June, monthly total depositions to Lake Superior are more uniformly distributed over the year with comparatively greater levels in cold months.

Description: [1]  The chemical discontinuity at the extratropical tropopause (ExTP) and stratosphere-troposphere exchange (STE) pathways are investigated using the long-lived chemical species carbon monoxide (CO) and ozone (O 3 ) measured by the AuraMicrowave Limb Sounder (MLS). A relative coordinate, tropopause latitude (TpLat), is developed based on potential vorticity (PV) from the Goddard Earth Observing System Version 5 (GEOS-5) data assimilation system. TpLat is defined as theshortest geographic distance along an isentropic surfacefrom the extratropical tropopause (ExTP) to an observation location. Our results show that this coordinate highlights the sharp chemical discontinuities at the ExTP more clearly than the widely-used equivalent latitude coordinate (EqLat). Geographical distributions of STE pathways and barriers are investigated based on meridional gradients in O 3 abundances in the new TpLat coordinate in conjunction with analysis of Rossby wave-breaking between 330 K and 360 K. In northern hemispheric (NH) winter (Dec-Jan-Feb), NH STE pathways are seen mainly above the northeast Pacific. In NH summer (Jun-Jul-Aug), the NH pathway covers all longitudes at 330 K. However, it is mainly located above Asia at 340 K and above the Atlantic and the North Pacific at 350 K and 360 K.In the southern hemisphere (SH), there is a weaker STE region above the Eastern Indian Ocean and the southwestern Pacific,at and above 350 K in SH winter, and a stronger STE region overthe Southeastern Pacificat these levels during SH summer. In addition, this study shows NH PV gradients are slightly stronger near the ExTP in summer than in winter even though the subtropical jet is weaker and Rossby-wave breaking is stronger in summer than in winter.

Description: [1]  It has been reported that Pi2 pulsations can be excited under extremely quiet geomagnetic conditions ( Kp  = 0). However, there have been few comprehensive reports of Pi2 pulsations in such a near ground state magnetosphere. To understand the characteristics of quiet-time Pi2 pulsations, we statistically examined Pi2 events observed on the nightside between 1800 and 0600 local time at the low-latitude Bohyun (BOH, L = 1.35) station in South Korea. We chose year 2008 for analysis because geomagnetic activity was unusually low in that year. A total of 982 Pi2 events were identified when Kp  ≤ 1. About 80% of the Pi2 pulsations had a period between 110 and 300 s, which significantly differs from the conventional Pi2 period from 40 to 150 s. Comparing Pi2 periods and solar wind conditions, we found that Pi2 periods decrease with increasing solar wind speed, consistent with the result of Troitskaya (1967). The observed wave properties are discussed in terms of plasmaspheric resonance, which has been proposed for Pi2 pulsations in the inner magnetosphere. We also found that Pi2 pulsations occur quasi-periodically with a repetition period of ~23–38 min. We will discuss what determines such a recurrence time of Pi2 pulsations under quiet geomagnetic conditions.

Description: On the basis of hypothetical particle-level mechanisms, several constitutive models of hydrate-bearing sediments have been proposed previously for gas production. However, to the best of our knowledge, the microstructural large-strain behaviors of hydrate-bearing sediments has not been reported to date because of the experimental challenges posed by the high-pressure and low-temperature testing conditions. Herein, a novel microtriaxial testing apparatus was developed, and the mechanical large strain behavior of hydrate-bearing sediments with various hydrate saturation values ( S h  = 0%, 39%, and 62%) were analyzed using microfocus X-ray computed tomography. Patchy hydrates were observed in the sediments at S h  = 39%. The obtained stress–strain relationships indicated strengthening with increasing hydrate saturation and a brittle failure mode of the hydrate-bearing sand. Localized deformations were quantified via image processing at the submillimeter and micrometer scale. Shear planes and particle deformation and/or rotation were detected, and the shear band thickness decreased with increasing hydrate saturation.

Description: The boundary between the upper and lower mantles of Earth corresponds to breakdown of (Mg,Fe)2SiO4, spinel (ringwoodite), into (Mg,Fe)SiO3 perovskite (pv) + (Mg,Fe)O, magnesiowüstite (mw). The rheology of these materials is important for understanding deeply subducted slabs, the termination of deep earthquakes, mantle convection, post-glacial rebound, etc. It has been proposed that decomposition of ringwoodite as subducting slabs enter the lower mantle leads to very fine-grained material that is inherently weak because it flows by grain-boundary sliding. Such abrupt and great weakening would have important geophysical implications. Here we test whether products from such decomposition are weak, using a realistic analogue high-pressure system (Co2TiO4). Our results show that spinel breakdown products are complicated intergrowths (symplectites) that flow by dislocation creep, rather than fine-grained domains that flow by diffusion creep as is commonly assumed from very fine phase domains seen in two dimensions. Application to Earth strongly suggests that ringwoodite breakdown is likely to strengthen the slab, reflecting the inherently greater viscosity of the uppermost lower mantle revealed by geophysical measurements.

Description: When an interplanetary (IP) shock passes over the Earth's magnetosphere, the geosynchronous magnetic field strength near noon is always enhanced except for the magnetopause crossing events. Near midnight, however, it increases or decreases. This indicates that the nightside magnetosphere is not always compressed by a sudden increase in the solar wind dynamic pressure. To understand midnight geosynchronous magnetic field responses to IP shocks, we statistically examined geosynchronous magnetic field perturbations, corresponding to 120 sudden commencements (SCs), observed when geosynchronous spacecraft were near midnight between 2200 and 0200 magnetic local times. Out of the 120 SCs, 107 SCs were identified by one geosynchronous spacecraft, and 13 SCs were identified by two geosynchronous spacecraft. Thus, 133 events were used in our statistical study. We observed 23 events in spring, 40 events in summer, 32 events in fall, and 38 events in winter, respectively. A statistical study of the midnight geosynchronous SC perturbations reveals the following characteristics. (1) In summer, all events show a positive enhancement (+Δ B T ) in the magnetic field strength. (2) In winter, however, Δ B T exhibits a positive (+Δ B T ) or negative (−Δ B T ) enhancement. (3) In summer, the midnight geosynchronous SC perturbations in the B H component (positive northward) in VDH coordinates are mostly (~88%, 35 out of 40 events) positive (+Δ B H ), while the occurrence rate of the positive perturbation (~43%) in the B z component (positive northward) in GSM coordinates is lower than that of the negative perturbation (~57%). (4) In winter, the negative perturbations in Δ B H (~61%) and Δ B z (~74%) are dominant. (5) Both the north-south components ( B H and B z ) in spring and fall are scattered around zero. To explain the observations we suggest that SC-associated cross-tail current ( J SC ) has a peak intensity around geosynchronous orbit thus is a main controlling factor of midnight geosynchronous magnetic field perturbations during SCs. Specifically, we suggest that the seasonal variation of the sign of Δ B H , Δ B z , and Δ B T is due to the seasonal variation of the spacecraft position relative to J SC .